Tai Chi has a lot of arm movements and combined with everything else, engages a lot of the torso. For a healthy person or someone with different types of health problems, this is fine. But for TOS, this can be problematic.

I had to start with 10 mins of seated Tai Chi for seniors and cripples, and build up from there. I used the Dr. Lam DVD that someone on here recommended. Found it on Amazon.

As much as I like Chinese martial arts, I would point a TOS person to focus on a "Fixing You" book and/or an Egoscue book. You can add the Tai Chi in after making progress with those.

HTH